This invention is related to a control system for vibratory conveyors and, more particularly, to a control system adaptable for use with vibratory systems having vibrating housings or surfaces of extended length for the conveying and/or treatment of articles in which the vibratory force is controlled over the entire length of the housing or surface.
There are a number of systems in which the vibratory motion providing direction and/or speed to material being conveyed by the conveyor is controlled. An example of such a system is set forth in U.S. Pat. No. 5,615,763 assigned to the same assignee of the present invention. As described therein with respect to one embodiment thereof, a pair of spaced shafts rotating in opposite directions are operatively coupled to a conveyor trough mounted on a stationary base through a plurality of isolating springs. The shafts have eccentrically mounted weights that are oriented such that the resultant force acting on the conveyor due to the rotation of the shafts and thus their associated weights goes through a maximum and minimum in a sinusoidal manner. The direction of the maximum resultant force is dependent upon the "relative phase angle" between the position of the rotating weights and a data plane. By varying the phase angle between the shafts, the direction or angle of attack of the resultant force can be changed so that the conveying rate and even the direction of the material on the conveyor can be changed. The invention in the aforementioned Patent addresses the problem of maintaining a predetermined phase angle for providing the desired angle of attack throughout an operating cycle of the conveyor through use of a control system. Such control system continuously measures the actual relative positioning of the weights, compares this to a programmed and predetermined positioning of the weights, and adjusts the speed of the motor driving one of the shafts until the actual positioning of the weights corresponds to the programmed positioning. Through the use of such a control system, the attack angle is maintained constant throughout the operating cycle of the conveyor.
While the above described system functions admirably for conveyors of standard and short lengths, many industries require extended treatment lengths of the material during processing. For example, long vibratory conveyors are frequently desired for heat transfer processing. When it is required to move material over such extended lengths such as, for example, spans exceeding about 30 feet, the use of a single unitary vibratory conveyor has heretofore been largely impractical. Extended length conveyors become unwieldy due, in part, to strength necessary to withstand the significant stress imposed on the frame of the conveyor by the vibratory system along its length. The size of the frame and concomitant cost become prohibitive. To address this problem, the manufacturers of vibratory equipment have found it necessary to employ two or more separate vibratory conveyors mounted end to end or having some technique of moving the material between the separated conveyors.
It is therefore a primary object of this present invention to provide a control system for a vibratory conveyor that permits the construction of a single unitary conveyor of extended length. It is still another important object of the present invention to provide for a control system for a vibratory conveyor that permits the tandem arrangement of a plurality of rotating shafts and eccentric weights to provide for a single angle of attack over the entire length of an extended unitary conveyor. It is still a further object of the present invention to provide for a control system for tumbling vibratory conveyors of extended lengths.